Determination of thermodynamic binding constants by affinity capillary electrophoresis

C. LANCIONI, S. KEUNCHKARIAN, C.B. CASTELLS Y L. GAGLIARDI

TALANTA

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018

0039-9140

A strategy to study thermodynamic binding constants by affinity capillary electrophoresis (ACE) is presented. Inorder to simplify mathematical treatment, analogy with acid-base dissociation equilibrium is proposed: insteadof ligand concentration [X], negative logarithm of ligand concentration (or activity), pX=-log[X], is used. Onthis base, and taking into account ionic activities, a general procedure for obtaining thermodynamic bindingconstants is proposed. In addition, the method provides electrophoretic mobilities of the free analyte and analyte-ligand complex, even when binding constants are low and thus, the complexed analyte fraction is also low.This is useful as a base to rationally analyze a diversity of situations, i.e., different mathematical dependenciesare obtained when analytes and ligands with different charges are combined. Practical considerations are givenfor carrying out a full experimental design.Enantiomeric ACE separation based on the use of chiral selectors is addressed. 2-hydroxypropyl-β-cyclodextrinwas chosen as a model ligand, and both enantiomeric forms of four pharmaceutical drugs (propranolol,pindolol, oxprenolol and homatropine methylbromide) were considered as model analytes. Practical aspects aredetailed and thermodynamic binding constants as well as free and complexed analytes mobilities are determined.